linux-kernel - [PATCH][next] openvswitch: check for null pointer return from nla_nest_start

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Message-Id: <20190501134158.15307-1-colin.king@canonical.com>
Date:   Wed,  1 May 2019 14:41:58 +0100
From:   Colin King <colin.king@...onical.com>
To:     Pravin B Shelar <pshelar@....org>,
        "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        dev@...nvswitch.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] openvswitch: check for null pointer return from nla_nest_start_noflag

From: Colin Ian King <colin.king@...onical.com>

The call to nla_nest_start_noflag can return null in the unlikely
event that nla_put returns -EMSGSIZE.  Check for this condition to
avoid a null pointer dereference on pointer nla_reply.

Addresses-Coverity: ("Dereference null return value")
Fixes: 11efd5cb04a1 ("openvswitch: Support conntrack zone limit")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 net/openvswitch/conntrack.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index c4128082f88b..333ec5f298fe 100644
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c
@@ -2175,6 +2175,10 @@ static int ovs_ct_limit_cmd_get(struct sk_buff *skb, struct genl_info *info)
 		return PTR_ERR(reply);
 
 	nla_reply = nla_nest_start_noflag(reply, OVS_CT_LIMIT_ATTR_ZONE_LIMIT);
+	if (!nla_reply) {
+		err = -EMSGSIZE;
+		goto exit_err;
+	}
 
 	if (a[OVS_CT_LIMIT_ATTR_ZONE_LIMIT]) {
 		err = ovs_ct_limit_get_zone_limit(
-- 
2.20.1